Profit Sharing, Retirement Savings Plans and Defined Benefit Pension Plans - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Provisions charged from operations for the profit sharing plan and retirement savings plans	$ 39.9	$ 42.9	$ 55.3
Contribution of common stock to profit sharing plan (in shares)	502,519	830,600	787,500
Defined benefit pension plan corridor rate	10.00%
Percentage of equity allocation, maximum	65.00%
Percentage of fixed income allocation, minimum	35.00%
Equity Security
Defined Benefit Plan Disclosure [Line Items]
Equity securities, minimum	40.00%
Equity securities, maximum	50.00%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Equity securities, minimum	50.00%
Equity securities, maximum	60.00%

Contribution toward common stock as part of contribution to the profit sharing plan.

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- Definition

Defined benefit plan corridor percentage.

+ References

No definition available.

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- Definition

Percentage of equity allocation maximum.

+ References

No definition available.

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- Definition

Percentage of fixed income allocation including cash minimum.

+ References

No definition available.

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- Definition

The amount of payment into the fund established for purposes of making future disbursements to the individual in accordance with the terms and understanding of the deferred compensation arrangement.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Target allocation maximum percentage of investments of this type to total plan assets presented on a weighted average basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)(i)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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- Definition

Target allocation minimum percentage of investments of this type to total plan assets presented on a weighted average basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)(i)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e2446-114920

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